1. Field of the Invention
The present invention generally relates to a wheel support bearing assembly for an automotive vehicle or the like and, more particularly, to the wheel support bearing assembly integrated with a magnetic encoder for detection of the number of revolution of a wheel.
2. Description of the Prior Art
As shown in FIG. 23, the wheel support bearing assembly is well known, which includes generally cylindrical inner and outer members 101 and 102 positioned one radially inside the other with an annular space defined therebetween, dual rows of rolling elements 103 interposed between the inner and outer members 101 and 102 and rollingly movably positioned within the annular space, an annular sealing device 105 accommodated within and positioned at one of opposite ends of the annular space, and an annular magnetic encoder 106 integrated together with the sealing device 105. This known wheel support bearing assembly is disclosed in, for example, the Japanese Laid-open Patent Publication No. 6-281018.
In this known wheel support bearing assembly, the sealing device 105 includes generally L-sectioned first and second annular sealing plates 107 and 108 press-fitted onto an outer periphery of the inner member 101 and into a bore of the outer member 102, respectively, and an annular sealing strip 109 secured to the second annular sealing plate 108. The first sealing plate 107 is generally referred to as a slinger. The annular magnetic encoder 106 employed therein is in the form of an elastic member (also referred to as a multi-pole magnet) 111 made of a vulcanizable elastic material mixed with a powdered magnetic material and is bonded by vulcanization to the first sealing plate 107. The multi-pole magnet 111 has a plurality of magnetic N- and S-poles alternately defined therein in a direction circumferentially thereof and is operatively associated with a magnetic sensor 110 disposed in face-to-face relation with the multi-pole magnet 111 to detect the number of revolutions of the wheel rotatably supported by the wheel support bearing assembly.
With the known wheel support bearing assembly of the structure discussed above, it has been found that in the event of ingress of foreign matter such as, for example, stones or rocks into a working gap delimited between the multi-pole magnet 111 and the magnetic sensor 110, the multi-pole magnet 111 and, hence, the magnetic encoder 106 may be impaired, resulting in failure to detect the number of revolutions of the wheel properly.
Accordingly, it is a primary object of the present invention to provide a wheel support assembly designed to prevent foreign matter from being caught in between the multi-pole magnet and the magnetic sensor and, if not at all, to render the multi-pole magnet to be little damaged.
In order to accomplish the foregoing object, the present invention in accordance with a first aspect thereof provides a wheel support bearing assembly which includes an outer member; an inner member positioned inside the outer member to define an annular space therebetween; at least one row of rolling element accommodated within the annular space and operatively interposed between the inner and outer members; a sealing device for sealing an open end of the annular space; and a protective cover made of a non-magnetic material.
The sealing device includes first and second annular sealing plates fitted to different members out of the inner and outer members. Each of the first and second sealing plate includes a generally cylindrical wall and a radial wall assembled together to represent a generally L-shaped section, the first and second sealing plates being positioned within the annular space in face-to-face relation with each other. The first sealing plate is fitted to a rotating member out of the inner and outer members with the radial wall of the first sealing plate positioned on one side adjacent an exterior of the bearing assembly. An annular multi-pole magnet having a plurality of different magnetic poles alternating in a direction circumferentially thereof is fitted to the radial wall of the first sealing plate. On the other hand, the second sealing plate includes a side sealing lip, slidingly engaged with the radial wall of the first sealing plate and opposedly extending radial sealing lips slidingly engaged with the cylindrical wall of the first sealing plate. The cylindrical wall of the second sealing plate is positioned adjacent a slight distance from a free edge of the radial wall of the first sealing plate with a slight radial gap defined therebetween. The protective cover referred to above is disposed exteriorly of the multi-pole magnet and positioned adjacent thereto with a predetermined air gap defined therebetween so that a number of revolution can be detected through the protective cover.
The multi-pole magnet referred to above may be in the form of a sintered magnet, or may be made of an elastic member, such as a rubber, or a plastics material mixed with a powdered magnetic material.
According to the first aspect of the present invention, since the protective cover is used and positioned exteriorly of the multi-pole magnet forming a part of the magnetic encoder so that the number of revolution can be detected through the protective cover, any possible xe2x80x9cbitingxe2x80x9d of foreign matter in between the magnetic sensor for the detection of the number of revolutions and the multi-pole magnet can be prevented by the presence of the protective cover. Also, even if the foreign matter is caught in between the protective cover and the magnetic sensor, the foreign matter does not directly contact the multi-pole magnet and, therefore, the multi-pole magnet is hardly damaged. Also, since the protective cover is positioned adjacent the multi-pole magnet forming the part of the magnetic encoder with the predetermined air gap intervening therebetween, rotation of the multi-pole magnet will not be disturbed by the protective cover. Yet, since the protective cover is made of the non-magnetic material, detection of the magnetic encoder by the magnetic sensor will not be disturbed undesirably.
In the first aspect of the present invention, the protective cover may be fitted to one of the first and second members that serves as a stationary member. With this design, the protective cover does not rotate and, since the protective cover and the magnetic sensor, both held stationary, confront with each other, the foreign matter can advantageously be prevented from entering in between the protective cover and the magnetic sensor during rotation.
Preferably, a slight labyrinth gap is defined between the protective cover and one of the first and second members that serves as a rotating member. The presence of the labyrinth seal is effective to avoid any possible ingress of dusts into the annular space between the inner and outer members through between the protective cover and the rotating member without the rotation of the rotating member being disturbed.
Also, a sealing lip may be provided, which is integrated with a radial edge of the protective cover and held in sliding contact with an end face of one of the inner and outer members that serves as a rotating member. The provision of the protective cover with the sealing lip is effective to avoid any possible ingress of the dusts into the annular space between the inner and outer members through between the protective cover and the rotating member.
The protective cover may be fitted to an outer periphery of the outer member. In this case, since the protective cover is mounted on the outer periphery of the outer member, unlike the case in which the protective cover is mounted on an inner periphery of the outer member, any possible space for disposition of the protective cover at an open end of the annular space between the inner and outer members can be dispensed with and a sufficient sectional height of the sealing device including the first and second sealing plate can advantageously be secured.
The protective cover may have a mounting portion, and further comprising a sealing rubber integrated with the mounting portion of the protective cover. This design is effective to avoid any possible ingress of dusts inwardly of the annular space between the inner and outer members from a mounting region of the protective cover.
According to a second aspect of the present invention, there is provided a wheel support bearing assembly similar to that provided for according to the above described first aspect of the present invention, but differing therefrom in that in the second aspect of the present invention that portion exteriorly of the multi-pole magnet is covered by the protective cover.
According to the second aspect of the present invention, since that portion exteriorly of the multi-pole magnet is covered by the protective cover of the non-magnetic material, any possible biting of the foreign matter in between the multi-pole magnet and the magnetic sensor can be avoided and, even if it occurs, there is no possibility of the multi-pole magnet being damaged. Since the protective cover is made of the non-magnetic material, the presence of the protective cover will not disturb detection performed by the magnetic sensor. Where the multi-pole magnet is made of an elastic member or a plastics material mixed with the powdered magnetic material, molding is easy to achieve and it can be molded to any desired shape such as, for example, forming an engagement portion cooperable with the radial wall of the sealing plate, and fitting to the radial wall can be performed easily. Where the multi-pole magnet is made of the elastic member such as a rubber, it can be bonded by vulcanization to the radial wall. Where the multi-pole magnet is made of the elastic member, although it appears that the multi-pole magnet is susceptible to damage in contact with the foreign matter since the elastic member is soft and flexible, the use of the protective cover intended to cover the multi-pole magnet is effective in avoiding any possible damage to the multi-pole magnet. Where the multi-pole magnet is in the form of the sintered magnet, it can provide an excellent magnetic force.
In the second aspect of the present invention, the protective cover may be fitted to one of the inner and outer members that serves as a rotating member.
Considering that the multi-pole magnet is mounted on the rotating member, fitting of the protective cover to the rotating member is effective to allow the protective cover to be disposed in contact with the multi-pole magnet without constituting any obstacle to rotation. For this reason, the presence of the protective cover between the multi-pole magnet and the magnetic sensor does not require the distance between the multi-pole magnet and the magnetic sensor to be increased for the rotation tolerance and there is no problem associated with reduction in detection output indicative of the number of revolutions.
Preferably, the protective cover may be of a generally L-sectioned shape including an upright wall, covering the multi-pole magnet, and a cylindrical wall fitted to one of the inner and outer members that serves as a rotating member, said first sealing plate being fitted to the cylindrical wall of the protective cover.
Where the protective cover is so configured and so shaped as to represent the generally L-sectioned shape, mere mounting of the cylindrical wall of the protective cover on the rotating member allows the protective cover as a whole to be mounted with the upright wall covering the multi-pole magnet. For this reason, the mounting of the protective cover can be firmly achieved by means of its cylindrical wall and can therefore be achieved easily.
An elastic sealing member may be interposed between the protective cover and one of the inner and outer members that serves as a rotating member. The presence of the elastic member between the protective cover and the rotating member is effective to enhance the sealing performance of the mounting region therebetween and to avoid any possible ingress of dusts and/or water from this mounting region into the annular space between the inner and outer members.
Preferably, the protective cover has an outer peripheral edge engaged with an outer peripheral edge of the radial wall of the first sealing plate. When the outer peripheral edge of the protective cover is engaged over the outer peripheral edge of the radial wall of the first sealing plate, the protective cover can easily be fitted to the rotating member. Also, since it is engaged with the upright wall where the multi-pole magnet is fitted, the protective cover can be firmly, but easily fitted so as to cover the multi-pole magnet.
In the practice of the second aspect of the present invention, the multi-pole magnet may have its opposite surfaces bonded respectively to the protective cover and the radial wall of the first sealing plate while being sandwiched between the protective cover and the radial wall of the first sealing plate. Where the multi-pole magnet is made of the elastic member such as a rubber, the bonding can be achieved by vulcanization. According to this design, when the multi-pole magnet is to be bonded to the first sealing plate, the protective cover can be bonded at the same time. For this reason, fitting of the protective cover to the rotating member can be simply and easily achieved.
According to a third aspect of the present invention, there is provided a wheel support bearing assembly which includes an outer member; an inner member positioned inside the outer member to define an annular space therebetween; at least one row of rolling element accommodated within the annular space and operatively interposed between the inner and outer members; a sealing device for sealing an open end of the annular space; a protective cover of a generally L-shaped section having an upright wall and a generally cylindrical wall both defined therein; and an annular multi-pole magnet having a plurality of different magnetic poles alternating in a direction circumferentially thereof and fitted to the radial wall of the first sealing plate secured to an inner face of the upright wall of the protective cover.
The sealing device includes first and second annular sealing plates fitted to different members out of the inner and outer members, each of the first and second sealing plate including a generally cylindrical wall and a radial wall assembled together to represent a generally L-shaped section, the first and second sealing plates being positioned within the annular space in face-to-face relation with each other. The first sealing plate is fitted to a rotating member out of the inner and outer members with the radial wall of the first sealing plate positioned on one side adjacent an exterior of the bearing assembly. The second sealing plate includes a side sealing lip, slidingly engaged with the radial wall of the first sealing plate and opposedly extending radial sealing lips slidingly engaged with the cylindrical wall of the first sealing plate, the cylindrical wall of the second sealing plate being positioned adjacent a slight distance from a free edge of the radial wall of the first sealing plate with a slight radial gap defined therebetween. The protective cover is positioned so as to confront the radial wall of the first sealing plate and the cylindrical wall of the protective cover is mounted on one of the first and second members that serves as a rotating member and wherein the cylindrical wall of the first sealing plate is mounted on the cylindrical wall of the protective cover.
According to the third aspect of the present invention, since the multi-pole magnet is provided on the inner face of the upright wall of the protective cover, the foreign matter possibly entering in the gap between the protective cover and the magnetic sensor will be caught in between the protective cover and the magnetic sensor and will not directly contact the multi-pole magnet. For this reason, there is no possibility that the multi-pole magnet may be damaged by the foreign matter so caught in therebetween. Since the protective cover is made of the non-magnetic material, the presence of the protective cover will not disturb detection of the multi-pole magnet. Also, since the multi-pole magnet is carried by the protective cover, the multi-pole magnet can be provided separate from the sealing plates of the sealing device and, therefore, the sealing device can easily be manufactured.
According to a fourth aspect of the present invention, there is provided a wheel support bearing assembly similar to that provided for according to the above described first aspect of the present invention, but differing therefrom in that in the fourth aspect of the present invention the protective cover is positioned outside the multi-pole magnet to cover an external portion of the multi-pole magnet and includes an outer peripheral edge portion bent to protrude axially inwardly of the annular space between the first and second members, and the outer peripheral edge portion of the protective cover is crimped over an outer peripheral edge of the radial wall of the first sealing plate.
According to the fourth aspect of the present invention, since a portion exteriorly of the multi-pole magnet is covered by the protective cover, any possible ingress of the foreign matter in between the multi-pole magnet and magnetic sensor if it occur do not lead to damages to the multi-pole magnet. Since the protective cover is made of the non-magnetic material, the presence of the protective cover does not disturb detection performed by the magnetic sensor. Also, since the protective cover is coupled with the first sealing plate with its outer peripheral edge portion crimped over the outer peripheral edge of the radial wall of the first sealing plate, the mounting is simple and firm and therefore, excellent in mass productivity.
In the present invention, the outer peripheral edge portion of the protective cover may have a plurality of cutouts defined therein at corresponding locations circumferentially thereof so as to extend inwardly thereof to thereby leave a corresponding number of pawls each positioned between the neighboring cut-outs, said pawls being crimped over the outer peripheral edge of the radial wall of the first sealing plate. Formation of the pawls by the presence of the cutouts in the outer peripheral edge portion of the protective cover is effective to facilitate the crimping work with the crimping width for each pawl being narrow.
Preferably, the protective cover may have an inner peripheral edge formed with a reinforcement rib. The provision of the reinforcement rib at the inner peripheral edge of the protective cover is effective to avoid any possible deformation of the inner peripheral edge of the protective cover during crimping of the outer peripheral edge portion thereof and, therefore, there is no possibility that the bondability of the protective cover to the multi-pole magnet may be reduced as a result of a possible deformation. In general the gap between the multi-pole magnet and the magnetic sensor confronting the multi-pole magnet is advantageously set to a very small gap in order to increase the magnetic characteristic by reducing the magnetic gap. For this reason, if the bondability of the protective cover to the multi-pole magnet is insufficient, interference with the magnetic sensor will occur and the gap cannot be set to a very small size. The problem associated with this interference resulting from the insufficient bondability can be eliminated by the presence of the reinforcement rib at the inner peripheral edge of the protective cover.
The protective cover preferably has a plate thickness within the range of 0.1 to 1.0 mm, preferably within the range of 0.2 to 1.0 mm, and more preferably within the range of 0.3 to 1.0 mm. Material for the protective cover is, for example, a metal sheet.
In order to minimize the magnetic gap between the multi-pole magnet and the magnetic sensor, the use of the protective cover of a thickness as small as possible is preferable. However, if the thickness is too small, the protective cover will lack a sufficient strength and the bondability between the multi-pole magnet and the protective cover will be lost as a result of deformation taking place during the crimping of the peripheral edge portion of the protective cover. If the thickness of the protective cover is not greater than 0.1 mm, there is the possibility of the protective cover being deformed as discussed above, but if it exceeds 1.0 mm, the magnetic gap will increase excessively.
The protective cover may be made of non-magnetic stainless steel and may have a Vickers hardness of not greater than Hv 200. If the protective cover is made of stainless steel, it can have a resistance to rusting and have an excellent strength. However, if the hardness exceeds Hv 200, there is the possibility that the protective cover may be deformed during crimping of the outer peripheral edge portion thereof. The stainless steel if not hardened exhibits a hardness of Hv 200.